Seven people were injured when a car bomb exploded in a shopping mall carpark in the popular Thai tourist island of Koh Samui on Friday. A major fire broke out at a Surat Thani retail and food complex at about the same time.

The Koh Samui blast came as over 80,000 tourists flood into the area for the Songkran festival this week.

Seven people, including a 12-year-old Thai-Italian girl, were injured in the blast. The bomb had been planted in a stolen car parked in an underground parking area of Central Festival department store. All of the wounded were later discharged from hospital with minor injuries.

Authorities are convinced the bombing is politically motivated, the Bangkok Sunday Nation reported. The fire is still being investigated.

Considering the timing of the bomb – shortly before the Songkran Festival – and its location in a busy tourist destination, the attack is considered to have been aimed at challenging the government.

In Phuket, security has been stepped up in tourism spots and department stores, especially Central Festival and the airport, following reports that cars stolen from southern border provinces would be moved to Phuket tomorrow, Phuket Governor Nisit Chansomwong said.

The army has ordered officials to increase surveillance at all checkpoints in Bangkok, especially spots favoured by Songkran revellers, such as Silom and Khao San roads.

Both the Nation newspaper and Bangkok Post published various opinions as to whether the attack was the work of anti-government protesters or Islamist insurgents from restive provinces in Thailand’s far south.

The consensus is that insurgents are unlikely to be behind it.

Security has been beefed up at popular tourist destinations in the south, including Phuket, Hat Yai and Samui.

Police have quite a few leads in the Koh Samui bombing and are pursuing them vigorously. They are checking whether the Koh Samui blast is linked to recent explosions near the Paragon shopping mall in Bangkok.

The fire at Surat Thani Co-operative, meanwhile, was brought under control by about 20 fire engines. Sompong Duangsuwan, a guard volunteer at the cooperative, said he heard six explosions before the fire spread, the Bangkok Post reported. Cooking-gas cylinders in the food centre exploded as firefighters were battling the blaze.